Looking at the conventional technology from the perspective of thickening or gelling oils, oil agent systems used in cosmetic compositions often contained silicone oils, but in such cases, the effect achieved by organic thickening/gelling agents was poor. Techniques for thickening or gelling oils can provide cosmetic composition manufacturers with a degree of freedom by which it is possible to arbitrarily control the form of a cosmetic composition from liquid to cream-form, paste-form, gel, solid, and the like, and are extremely important techniques. As a result, there has been an increase in the development of modified silicone-based thickening agents and gelling agents that are also advantageous in terms of feeling to touch and also an increase in research into using these thickening agents and gelling agents in cosmetic compositions.
The technique of solidifying oil agents by means of wax-form alkyl-modified silicones was known from the past, but this technique generally caused problems such as an increase in oiliness and a deterioration in spreadability and feeling to touch, the degree of freedom in controlling the form, viscosity and the like of a cosmetic composition being relatively low, and solidification readily occurring regardless of the added amount of the wax-form alkyl-modified silicone.
In addition, a gel silicone composition obtained by gelling a silicone oil using a polyether-modified silicone and water has been developed (see Patent Document 7), but this technique had the problem of the thickening/gelling effect being insufficient when an organic oil was contained in an oil agent system. In addition, this technique had problems in terms of feeling to touch, such as greasiness.
Meanwhile, there have been reports of techniques for gelling oils by means of amino acid derivative-modified silicones, straight chain polyamide-modified silicones, and the like, and the use of such techniques in cosmetic compositions. (Patent Documents 8 to 11 and so on) These gelling agents were excellent in terms of feeling to touch, but had a tendency to readily cause solidification regardless of the added amount of the gelling agent and involved the problem of difficulty in freely controlling the form, viscosity, and the like of a cosmetic composition. In addition, because of the gel being overly hard and solid, if the surface of the gel was scratched, the scratch remained on the surface and the appearance of the gel was impaired because it was not possible to restore the surface of the gel to a smooth state.
That is, silicone-based oil gelling agents of most conventional technology were of a type that solidified oils, and excellent oil thickening agents by which it was possible to freely control the form, viscosity, and the like of an oil or cosmetic composition according to the added amount of the thickening agent were not known. Furthermore, materials and techniques able to stably thicken a variety of oil agent systems containing combinations of silicone oils and organic oils were also not known.
Next, as an explanation of the conventional technology in terms of the relationship between a (poly)glycerin-modified silicone and oil thickening/gelling techniques, cosmetic compositions obtained by combining a silicone branched polyhydric alcohol-modified silicone (for example, an alkyl/linear siloxane branch/polyglycerin co-modified silicone) with an organo-modified clay mineral or a fructooligosaccharide fatty acid ester, which are known as oil thickening/gelling agents (see Patent Documents 12 and 13), a makeup cosmetic composition material that contains specific proportions of an alkyl glyceryl ether-modified silicone having a specific structure and silicic anhydride, which is known as an oil thickening/gelling agent (see Patent Document 14), and the like have been proposed.
The (poly)glycerin-modified silicones used in these techniques have poor oil thickening/gelling capacity, and must therefore be used in combination with another material capable of effectively thickening or gelling an oil agent, and had the problem of the effect of controlling the viscosity or form required for a cosmetic composition being unsatisfactory. In addition, organo-modified clay minerals and silicic anhydride can cause aggregation depending on the type of oil agent or the water content, and the proposed cosmetic compositions had problems in terms of stability. Fructooligosaccharide fatty acid esters exhibited insufficient capacity for thickening/gelling silicone oils other than cyclic siloxanes, and had the problem of reduced freedom when formulating cosmetic compositions.
Recently, Patent Document 15 has proposed a novel alternating copolymer of organopolysiloxane with polyglycerin derivative, and suggests that a high molecular weight polyglycerin-modified silicone can be obtained without the problem of white turbidness and the like, caused by the unreacted raw material occurring. However, it is clear from the chemical structure that this compound has a hydrophilic group portion incorporated on its backbone. As a result, this copolymer has properties completely different from those of conventional general-use hydrophilic silicones such as polyether-modified silicones and the like and, therefore a high level of technical skill is necessary to stably compound this copolymer in delicate formulations such as cosmetic products and the like, leading to the problem of the field of use being limited. Furthermore, this copolymer has good compatibility with oil agents comprising only silicone-based oils, but readily undergoes phase separation in mixed oil agent systems comprising silicone-based oils and organic oils, and had the problem of being unable to achieve a satisfactory effect.
The cause of such problems is closely related to problems in production techniques of conventional polyhydric alcohol-modified silicone. That is, silicones modified by polyhydric alcohols such as (poly)glycerin had a low degree of freedom in terms of structural design and were difficult to produce with stable product quality. Such polyhydric alcohol-modified silicones are ordinarily produced by adding a polyhydric alcohol derivative having a reactive unsaturated group to an organohydrogensiloxane. However, in many cases, compatibility between the remaining polyhydric alcohol derivative and the copolymer that is a reaction product is low, and such silicones separate into two phases within a short period of time following production, meaning that there were significant constraints when mass producing such silicones.
Additionally, compatibility between organohydrogensiloxanes and such polyhydric alcohol derivatives is fundamentally low and, therefore, when the design is such that molecular weight of the copolymer exceeds about 5,000, the addition reaction does not complete even if a solvent is added, thus, in many cases, leading to difficulties in producing the target product. Even when the molecular weight is about 3,000, the unreacted product gradually separates or precipitates. This necessitates a task of removing the separated or precipitated material and is a large obstruction from the perspective of production efficiency as well. (Patent Documents 16 to 18)
Even when a compound is used in which a form of the hydroxyl group is protected as the polyhydric alcohol derivative, deprotection is required following completion of the reaction and, therefore, the problem of separation into two phases cannot be avoided. In addition, heavy acidizing conditions must be introduced in order to achieve deprotection in this method, and the desired product, such as one having a low molecular weight, cannot be obtained in an easily reproducible manner as a result of disconnections of the silicone backbone occurring. (Patent Document 19)
Patent Document 20 proposes a method for producing a branched polyglycerol-modified silicone obtained by adding/graft polymerizing a silicone having at least one functional group selected from the group consisting of hydroxy groups, carboxy groups, amino groups, imino groups, mercapto groups, and epoxy groups, with 2,3-epoxy-1-propanol in the presence of an acidic or basic catalyst. However, with this method, the siloxane backbone disconnects during the graft polymerization, which results in two or more components having different properties being prone to be produced as the copolymer. This led to a multitude of problems related to product quality, refining processes, and the like.
For these reasons, because few conventional polyhydric alcohol-modified silicone are of practical use and are limited in terms of production techniques, most applied research has related to low molecular weight polyhydric alcohol-modified silicones. Examples of research into the use of high molecular weight polyglycerin-modified silicones, such as those having molecular weights in excess of 15,000, in cosmetic compositions cannot be found, except for Patent Document 15, which relates to a block copolymer, and in particular, there are no examples of reports into the use in cosmetic compositions of high molecular weight silicones in which a side chain and/or terminal of the polysiloxane backbone is modified by a polyglycerin derivative.
On the other hand, white pigments such as titanium oxide and zinc oxide, coloring pigments such as red iron oxide, and powders such as mica, sericite, and the like are widely used as basic cosmetic products, rouges, sunscreens, nail colors, nail coatings, foundations, mascaras, eye liners, and similar cosmetic compositions. Reasons for compounding these powders in cosmetic compositions include adjusting the hue, covering properties and feeling to touch of a cosmetic composition, and examples in which these powders have been combined with conventional polyhydric alcohol-modified silicones and used in oil-based cosmetic compositions have been reported. (Patent Documents 1 to 6 and 12 to 14)
However, aggregation or sedimentation of the powder readily occurred in these techniques, and it was not possible to give the user sufficient satisfaction for reasons such as coating unevenness or insufficient covering properties when applied to the skin or unnatural hues. In addition, the polyhydric alcohol-modified silicone used has a low molecular weight and poor oil thickening properties, and is therefore unsatisfactory in terms of cosmetic retainability.
Among powders, silicone-based powders such as organopolysiloxane elastomer spherical powders, poly(methyl silsesquioxane) powders, silicone resin powders, and silicone rubber powders and organic resin powders such as silk powders, nylon powders, poly(methyl methacrylate) powders, and polyethylene powders are excellent in terms of oil absorption capacity, and therefore mitigate the strong oiliness inherent in oil-based cosmetic compositions and the like and achieve the effect of making the skin sensation/feeling more natural following application. However, such powders were difficult to disperse uniformly in formulations and caused problems such as formulations feeling powdery as the compounded amount of the powder increased.
Therefore, there was a need for a material and/or cosmetic composition which can uniformly and stably disperse/solidify a powder or colorant in an oil-based cosmetic composition and which can maintain an excellent cosmetic effect and a natural feeling on the skin with no discomfort for approximately 1 day after the oil-based cosmetic composition is applied to the skin.
Finally, an explanation will be given of the conventional technology that relates to silicone-containing gel compositions. Interest has been shown in gel cosmetic compositions in terms of characteristics and effects based on the physical structures thereof, and a variety of investigations have been carried out. Although linked to oil thickening/gelling techniques, cosmetic compositions often have the problem of being difficult to use when in a form that is completely solid or a liquid having a low viscosity, meaning that the scope of application is limited. As a result, gel cosmetic compositions having an intermediate viscosity or elasticity between a liquid and a solid and development of materials and techniques able to control cosmetic compositions in these forms are needed.
Therefore, among numerous techniques for thickening/gelling oils, the technique disclosed in Patent Document 7 of a gel silicone composition can greatly thicken or gel a silicone oil that is an oil agent having a high compounding content in a cosmetic composition and exhibits good compositional stability compared to cases in which a powdery gelling agent is used, and is widely used as a base for a gel cosmetic composition or a base for an emulsion composition or emulsion cosmetic composition. (Patent Documents 21 to 26)
However, the polyether-modified silicone used as a thickening/gelling agent in Patent Document 7 must contain water in order for gelling to be possible, and therefore had the problem of the range of formulations being limited and had concerns regarding stickiness and greasiness depending on the compounded amount of the polyether-modified silicone. Furthermore, in cases where an oil agent system contains an organic oil, the thickening/gelling effect was poor.
In addition to silicone oils, a variety of oil agents such as hydrocarbon oils and ester oils are used in cosmetic compositions, and these oil agents are often additionally used in cosmetic composition formulations in order to make use of each oil agent's advantages and make up for each oil agent's drawbacks in terms of feeling to touch and the like. Therefore, there is a need for a gel cosmetic composition in which a variety of oil agent systems comprising a combination of a silicone oil and an organic oil can be maintained in a gel form having an intermediate viscoelasticity between a liquid and a solid. In addition, there is a need for a gel cosmetic composition in which the form, viscosity and the like of the gel cosmetic composition can be freely controlled by adjusting the added amount of the thickening/gelling agent.    Patent Document 1: Japanese Patent No. 3389271 (Japanese Unexamined Patent Application Publication No. H-06-157236)    Patent Document 2: Japanese Patent No. 3513682 (Japanese Unexamined Patent Application Publication No. H-09-71504)    Patent Document 3: Japanese Patent No. 3625471 (WO2003-075864)    Patent Document 4: Japanese Unexamined Patent Application Publication No. H-06-305933 (Japanese Patent No. 3477222)    Patent Document 5: Japanese Unexamined Patent Application Publication No. H-07-25728 (Japanese Patent No. 3160427)    Patent Document 6: Japanese Unexamined Patent Application Publication No. H-07-33622 (Japanese Patent No. 3200247)    Patent Document 7: Japanese Patent No. 3333782 (Japanese Unexamined Patent Application Publication No. H-05-311076)    Patent Document 8: Japanese Unexamined Patent Application Publication No. 2004-182680    Patent Document 9: U.S. Pat. No. 5,874,069    Patent Document 10: U.S. Pat. No. 5,919,441    Patent Document 11: U.S. Pat. No. 6,534,072    Patent Document 12: Japanese Patent No. 3678420 (WO2003-041664)    Patent Document 13: Japanese Unexamined Patent Application Publication No. 2004-231608    Patent Document 14: Japanese Unexamined Patent Application Publication No. 2005-194523    Patent Document 15: Japanese Unexamined Patent Application Publication No. 2005-42097    Patent Document 16: Japanese Patent Publication No. S-62-34039    Patent Document 17: Japanese Patent No. 3976226 (Japanese Unexamined Patent Application Publication No. 2002-179798)    Patent Document 18: Japanese Unexamined Patent Application Publication No. 2005-089494    Patent Document 19: Japanese Patent Publication No. H-06-089147 (Japanese Patent No. 1956013)    Patent Document 20: Japanese Unexamined Patent Application Publication No. 2004-339244    Patent Document 21: Japanese Patent No. 3639315 (Japanese Unexamined Patent Application Publication No. H-07-100358)    Patent Document 22: Japanese Patent No. 3407770 (Japanese Unexamined Patent Application Publication No. H-08-217626)    Patent Document 23: Japanese Patent No. 3719540 (Japanese Unexamined Patent Application Publication No. H-09-194323)    Patent Document 24: Japanese Patent No. 3580384 (Japanese Unexamined Patent Application Publication No. H-08-268831)    Patent Document 25: Japanese Patent No. 3580385 (Japanese Unexamined Patent Application Publication No. H-08-268832)    Patent Document 26: Japanese Patent No. 3313043 (Japanese Unexamined Patent Application Publication No. H-10-245317)